1. Field of the Invention
The present invention generally relates to recording apparatuses of helical scan type, and more particularly, to a rotary head-type magnetic recording apparatus such as rotary head-type digital audio tape recorder (referred to as R-DAT hereinafter), and to a manufacturing method of a rotary head used therein.
2. Description of the Background Art
FIG. 8 is a plan view showing structure of a rotating drum 31 in a conventional R-DAT. The rotating drum 31 has two writing heads 32a and 32b mounted thereon 180.degree. apart from each other. The two writing heads 32a and 32b are set to have azimuth angles of +20.degree. and -20.degree., respectively. Also, the rotating drum 31 is provided with two reproducing heads 33a and 33b spaced 180.degree. apart from each other. The azimuth angles of the two reproducing heads 33a and 33b are also set to be +20.degree. and -20.degree., respectively. The four heads above are arranged to be spaced 90.degree. apart from one another. The rotating drum 31 has diameter D1 of 30 mm and has a magnetic tape 34 contacted thereon with the support of two guide pins 35 and 36. The contact angle of this magnetic tape 34 to the rotating drum 31 is set to 90.degree.. With such a structure, the rotating drum 31 rotates in the direction of arrow 37, while recording on or reproducing from the magnetic tape 34 which is run in the direction of arrow 38.
When an R-DAT is used as an auxiliary storage apparatus of a computer or the like, a read-after-write operation is performed in order to enhance reliability of the data being recorded. That is, immediately after a recording, the recorded data is read out to examine whether or not the data has been correctly recorded.
FIG. 9 is a timing chart showing the read-after-write operation in the structure shown in FIG. 8. Since writing heads 32a and 32b and corresponding reproducing heads 33a and 33b are arranged to be spaced 90.degree. apart from one another and also the contact angle of magnetic tape 34 to rotating drum 31 is 90.degree., a reading operation is performed immediately after a writing operation is completed.
In order to make the above-described structure of R-DAT compact, it has been proposed to make the diameter of rotating drum 31 smaller. FIG. 10 is a plan view showing another structure of rotating drum 31, where diameter D4 is 20 mm. In FIG. 10, the parts corresponding to those in FIG. 8 are designated by the same reference numerals. The reduction of 10 mm in diameter of rotating drum 31 necessitates also a reduction of 135.degree. in the contact angle of magnetic tape 34 to rotating drum 31.
FIG. 11 is a timing chart showing the read-after-write operation in the structure shown in FIG. 10. Though writing heads 32a and 32b and corresponding reproducing heads 33a and 33b are arranged to be spaced 90.degree. apart from one another, the writing operation and the reading operation have to be performed partially during the same periods due to the contact angle 135.degree. of magnetic tape 34 to rotating drum 31. As a result, there arises a problem of crosstalk defined as the transfer of a writing signal into the reading operation.